There has been heretofore known a structure for coupling a side member disposed in a longitudinal direction of a vehicle body to a cross member disposed in a transverse direction of a vehicle body by use of a gusset (as the prior art, see Japanese Utility Model Laid-Open Nos. H5 (1993)-58569 and H4 (1992)-51871).
For example, as shown in FIGS. 5A and 5B, a side member 101 has an approximately U-shaped cross section including a vertical wall 102 and upper and lower horizontal walls 103 and 104. The upper and lower horizontal walls 103 and 104 are bent from upper and lower ends of the vertical wall 102, respectively, and extend inward in a vehicle transverse direction. A cross member 105 has an approximately U-shaped cross section including a side wall 106, an upper wall 107 and a lower wall 108. The upper and lower walls 107 and 108 are bent from upper and lower ends of the side wall 106, respectively, and extend toward one end in a longitudinal direction of a vehicle body. A gusset 109 has a vertical plate 110 and upper and lower horizontal plates 111 and 112. The vertical plate 110 is fixed to the vertical wall 102 of the side member 101. The upper and lower horizontal plates 111 and 112 are bent from upper and lower ends of the vertical plate 110, respectively, and extend inward in the vehicle transverse direction. The upper and lower horizontal plates 111 and 112 are fixed to the upper and lower walls 107 and 108 of the cross member 105, respectively.
The upper and lower horizontal walls 103 and 104 of the side member 101 and the upper and lower walls 107 and 108 of the cross member 105 are not directly coupled together by use of rivets or the like but are coupled together by use of the gusset 109. Thus, there exist no rivets or the like, which project from upper and lower surfaces of the upper and lower horizontal walls 103 and 104 of the side member 101. Accordingly, the upper and lower surfaces of the horizontal walls 103 and 104 can be maintained in a flat state. Consequently, it is possible to effectively utilize a space in a vehicle height direction.
On an outer surface of the vertical wall 102 of the side member 101 in the vehicle transverse direction, a mounting plate part 114 of a leaf spring bracket 113 for supporting a suspension mechanism (not shown) is fixed. Thus, the leaf spring bracket 113 is fixed to a coupled portion of the side and cross members 101 and 105. This is in order to securely support the suspension mechanism by dispersing load acting thereon to the side and cross members 101 and 105.
Moreover, it is required to firmly support the gusset 109 by use of the side member 101. Thus, the vertical plate 110 of the gusset 109 is fixed to the vertical wall 102 of the side member 101 in a state of coming into surface contact with an inner surface of the vertical wall 102 in the vehicle transverse direction. Consequently, it is structurally difficult to fix the gusset 109 and the leaf spring bracket 113, which are disposed so as to face each other while sandwiching the side member 101 therebetween, to the vertical wall 102 individually. For example, when the gusset 109 is fixed to the vertical wall 102 of the side member 101 after fixing the leaf spring bracket 113 to the vertical wall 102 by use of the rivets, parts of the rivets fixing the leaf spring bracket 113, the parts projecting from the inner surface of the vertical wall 102 in the vehicle transverse direction, interfere with the vertical plate 110 of the gusset 109. Thus, the surface contact state of the vertical plate 110 and the vertical wall 102 of the side member 101 cannot be obtained. From the above-described reason, the mounting plate part 114 of the leaf spring bracket 113 is fixed to the vertical wall 102 of the side member 101 by use of rivets 115 for fixing the vertical plate 110 of the gusset 109.
However, as described above, in the structure in which the vertical plate 110 of the gusset 109 and the mounting plate part 114 of the leaf spring bracket 113 are fastened together by use of the common rivets 115 and fixed to the vertical wall 102 of the side member 101, it is required to assemble these three members while simultaneously positioning the members. Thus, an assembly operation thereof is complicated.
As a structure for solving the inconvenience described above, for example, as shown in FIGS. 6A and 6B, there is one in which a gusset 116 is formed of an upper gusset 117 and a lower gusset 118.
The upper gusset 117 has an upper vertical plate 119 and an upper horizontal plate 120. The upper vertical plate 119 is fixed to the vertical wall 102 of the side member 101. The upper horizontal plate 120 is bent from an upper end of the upper vertical plate 119, extends inward in the vehicle transverse direction, and is fixed to the upper wall 107 of the cross member 105. The lower gusset 118 has a lower vertical plate 121 and a lower horizontal plate 122. The lower vertical plate 121 is fixed to the vertical wall 102 of the side member 101. The lower horizontal plate 122 is bent from a lower end of the lower vertical plate 121, extends inward in the vehicle transverse direction, and is fixed to the lower wall 108 of the cross member 105. The upper and lower horizontal plates 120 and 122 of the gusset 116 are fixed to the vertical wall 102 of the side member 101 by use of dedicated rivets 123 and 124, respectively. The mounting horizontal plate 114 of the leaf spring bracket 113 is fixed to the vertical wall 102 of the side member by use of dedicated rivets 125 disposed between the upper and lower horizontal plates 120 and 122.
According to the foregoing configuration, the upper and lower gussets 117 and 118 are each fixed to the cross member 105 in advance, and the leaf spring bracket 113 is fixed to the side member 101 by use of the rivets 125. Thereafter, the upper and lower gussets 117 and 118 are fixed to the side member 101 by use of the rivets 123 and 124, respectively. Specifically, after the cross member 105 and the upper and lower gussets 117 and 118 are assembled as one unit and the side member 101 and the leaf spring bracket 113 are assembled as one unit, the both units can be combined together. Therefore, compared to the case where the three members are simultaneously assembled as shown in FIGS. 5A and 5B, assembly workability is more improved.
However, in the case where the gusset 116 is formed of two separate components of the upper gusset 117 and the lower gusset 118 as shown in FIGS. 6A and 6B, it is undeniable that rigidity of the gusset 116 is lowered compared to the case of using the one gusset 109 as shown in FIGS. 5A and 5B. Therefore, in order to ensure rigidity in the coupled portion of the side and cross members 101 and 105, particularly, torsional rigidity in a direction of rotation about the cross member 105, reinforcing members may be required additionally. Thus, an increase in the number of components, an increase in weight and a complication of the structure and the like may be induced.
The present invention was made in consideration of the circumstances described above. An object of the present invention is to provide a coupling structure of side and cross members, which is capable of providing sufficient rigidity without inducing an increase in weight and a complication of the structure and provides excellent assembly workability.